android主线程和子线程之间消息传递详解
从主线程发送消息到子线程（准确地说应该是非UI线程）
packagecom.zhuozhuo;
importandroid.app.Activity;
importandroid.os.Bundle;
importandroid.os.Handler;
importandroid.os.Looper;
importandroid.os.Message;
importandroid.util.Log;
importandroid.view.View;
importandroid.view.View.OnClickListener;
publicclassLooperThreadActivityextendsActivity{
/**Calledwhentheactivityisfirstcreated.*/
privatefinalintMSG_HELLO=0;
privateHandlermHandler;
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
newCustomThread().start();//新建并启动CustomThread实例
findViewById(R.id.send_btn).setOnClickListener(newOnClickListener(){
@Override
publicvoidonClick(Viewv){//点击界面时发送消息
Stringstr="hello";
Log.d("Test","MainThreadisreadytosendmsg:"+str);
mHandler.obtainMessage(MSG_HELLO,str).sendToTarget();//发送消息到CustomThread实例
}
});
}
classCustomThreadextendsThread{
@Override
publicvoidrun(){
//建立消息循环的步骤
Looper.prepare();//1、初始化Looper
mHandler=newHandler(){//2、绑定handler到CustomThread实例的Looper对象
publicvoidhandleMessage(Messagemsg){//3、定义处理消息的方法
switch(msg.what){
caseMSG_HELLO:
Log.d("Test","CustomThreadreceivemsg:"+(String)msg.obj);
}
}
};
Looper.loop();//4、启动消息循环
}
}
}
从非UI线程传递消息到UI线程(界面主线程），因为主界面已经有MessageQueue，所以可以直接获取消息处理消息。而上面由主线程向非UI线程中处理消息的时候，非UI线程需要先添加消息队列，然后处理消息循环。
publicclassThreadHandlerActivityextendsActivity{
/**Calledwhentheactivityisfirstcreated.*/
privatestaticfinalintMSG_SUCCESS=0;//获取图片成功的标识
privatestaticfinalintMSG_FAILURE=1;//获取图片失败的标识
privateImageViewmImageView;
privateButtonmButton;
privateThreadmThread;
privateHandlermHandler=newHandler(){
publicvoidhandleMessage(Messagemsg){//此方法在ui线程运行
switch(msg.what){
caseMSG_SUCCESS:
mImageView.setImageBitmap((Bitmap)msg.obj);//imageview显示从网络获取到的logo
Toast.makeText(getApplication(),getApplication().getString(R.string.get_pic_success),Toast.LENGTH_LONG).show();
break;
caseMSG_FAILURE:
Toast.makeText(getApplication(),getApplication().getString(R.string.get_pic_failure),Toast.LENGTH_LONG).show();
break;
}
}
};
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mImageView=(ImageView)findViewById(R.id.imageView);//显示图片的ImageView
mButton=(Button)findViewById(R.id.button);
mButton.setOnClickListener(newOnClickListener(){
@Override
publicvoidonClick(Viewv){
if(mThread==null){
mThread=newThread(runnable);
mThread.start();//线程启动
}
else{
Toast.makeText(getApplication(),getApplication().getString(R.string.thread_started),Toast.LENGTH_LONG).show();
}
}
});
}
Runnablerunnable=newRunnable(){
@Override
publicvoidrun(){//run()在新的线程中运行
HttpClienthc=newDefaultHttpClient();
HttpGethg=newHttpGet("http://csdnimg.cn/www/images/csdnindex_logo.gif");//获取csdn的logo
finalBitmapbm;
try{
HttpResponsehr=hc.execute(hg);
bm=BitmapFactory.decodeStream(hr.getEntity().getContent());
}catch(Exceptione){
mHandler.obtainMessage(MSG_FAILURE).sendToTarget();//获取图片失败
return;
}
mHandler.obtainMessage(MSG_SUCCESS,bm).sendToTarget();//获取图片成功，向ui线程发送MSG_SUCCESS标识和bitmap对象
//mImageView.setImageBitmap(bm);//出错！不能在非ui线程操作ui元素
//mImageView.post(newRunnable(){//另外一种更简洁的发送消息给ui线程的方法。
//
//@Override
//publicvoidrun(){//run()方法会在ui线程执行
//mImageView.setImageBitmap(bm);
//}
//});
}
};
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持毛票票。